SolvedCH51575 | Assessing Time Limits: The Time Limits: When the new time limits take effect: Insurance premium tax, aggregates levy, climate change levy and landfill tax - extended time limits and transitional provisions
From HM Revenue & Customs · Compliance Handbook
From 1 April 2010 you can make an assessment up to 20 years from the end of
the accounting period (for aggregates levy and climate change levy),
the relevant event (for insurance premium tax and landfill tax), or
the failure or event giving rise to a penalty.
You can only do this in limited circumstances. You can find more detail at CH53600, but briefly this is where tax has been lost because
of deliberate behaviour, or
the person failed to comply with a notification obligation.
Exception
For aggregates levy, climate change levy and landfill tax, if you rely upon the 20-year time limit to assess an accounting period or relevant event ending on or before 31 March 2011 to recover tax lost because the person failed to comply with a notification obligation, you can only do so if the failure gives rise to a penalty.
There is no such requirement where you use the 20-year time limit to assess an accounting period or relevant event ending on or after 1 April 2010.